3.1 Circular Motion

Question 2

What is a period of rotation?

Answer 2

The period of rotation is the time it takes for an object to complete one rotation or oscillation. For circular motion, this means it is the time it takes for the object to make one whole revolution.

Question 3

What is frequency?

Answer 3

The number of times an object completes a full rotation or oscillation in a unit time is the frequency.

Question 4

What is a radian?

Answer 4

The angle of a circle sector such that the radius is equal to the arc length.

• Radians are usually written in terms of 𝝅
• 2𝝅 radians = 360 degrees

Question 5

What kind of force is required to keep an object moving in a circle at constant speed?

Answer 5

A force that is always applied towards the centre of a circular path. It is known as a centripetal force.

Question 6

An object moving in a circle at a constant speed is accelerating. True or False?

Answer 6

• True
• The direction is always changing hence the velocity always changing. Acceleration is defined as the change in velocity over time.

Question 7

What equation(s) can you use to calculate the magnitude of angular speed (⍵)?

Answer 7

⍵ = v/r or ⍵ = 2𝝅ƒ
⍵: s−1
v: ms−1, r: m, f: Hz

Question 8

What is angular acceleration in terms of angular velocity?

Answer 8

• a = ⍵^2r
• ⍵: s−1 a: ms−2 r: m

Question 9

What is angular acceleration in terms of velocity?

Answer 9

• a = v^2/r
• a: ms−2 v: ms−1 r: m

Question 10

What are the equations for centripetal force?

Answer 10

• F = mv^2/r or F = m⍵^2r
  ⍵: s−1 v: ms−1
  r: m F: N m: kg

Question 11

What are the conditions for SHM?

Answer 11

● Acceleration must be proportional to its displacement from the equilibrium point.
● It must act towards the equilibrium point.
● a ∝ -𝑥

Question 12

What is the constant of proportionality linking acceleration and 𝑥?

Answer 12

⍵^2 or - k/m

Question 13

What is 𝑥 as a trig function of t and ⍵?

Answer 13

• 𝑥= Acos(⍵t) or 𝑥= Asin(⍵t)
  ⍵: s−1 A: m x: m t: s

Question 14

How can you calculate the maximum speed using ⍵ and A?

Answer 14

Max speed = ⍵A ⍵: s−1
A: m

Question 15

How can you calculate the maximum acceleration using ⍵ and A?

Answer 15

Max acceleration =⍵^2A ⍵: s−1
A: m